Variable air condenser



Julie 5,- 1928.

1,6?Z,367 A. D. CARDWELL VARIABLE AiR COND NSER Filed NEW. 12, 19255-Sheets-Sheet 1 u 91:21:1 I I O '1 INVENTGR flilen L (ardwez'l BY 7\\ HATTORNEY June 5, 1928. 4 1,672,367

. .A. D. CARDWELL VARIABLE 'Ain CONDENSER Filed Nd vyl 1925' aSheets-$heet I 2 p: 6 4:9 7 /r 4 Y 5-1. 7 22 A? 7 filler? 0. Car/wellATTORNEY June 5, 1928.

- A. D. CARDWELL VARIABLE AIR CONDENSER Filed Nov. 12,1925-- sSheets-Sheet '3 .INVENTOR Allen 0. (a/"dwell V 7% Arronnzv Patented June 5, 19 28.

ALLEN I). CARDWELL, OF RQCK'VILLE GEN'XEB, NEW YGRK.

VAEIABLE AIR ClQNDENSER.

Application. filed November 12, 1925. Serial Ito. 8,548.

Myinvention relates to improvements in the class of ele'tricalcondensers in .which series of platesare movable relatively to anotherfor varying the capacit of the con denser,., such as for straight linefrequency variation or straight line Wave length variation, tc. In theusual forms oi such condensers havin rotors, as knownto me, thethickness of t e dielectric between the movable and stationary platesremains constant in their different positions of adjustment and theincrease in capacity is linear in accordance with the effective oropposing areas of the lates. o ject of my invention is to vary thethickness of the dielectrics between opposing plates in differentoperative positions of the 'olatesfor varying the capacity of thecondenser in addition to the usual variation of the capacity due tovariation of the interleaving of the plates. I

In carrying out my invention I provide plates of the condenser of such aform that when the plates of the movable element or 2 rotor approach theplates of the stationary element or stator, as at minimum positions, theair dielectrics between the plates may be relatively large, and astheplates interleave to a greater extent'the thickness of the air adielectric between the plates of the. several elements will decrease, sothat as theplates approach or reach the maximum interleaving peositionsthe thickness tween the plates will be minimum, and conversely as theplates are movedftrom maximum to minimum capacity positions;

other Words, in accordance with my invention when the effectiveareabetwecnjthe plates of the different elements is increased inearlyand the capacity correspondingly increased by reason of the interleavingof the platesthe capacity of the condenser will be further increased ingreater proportion as the surfaces of the other. The decrease of thethickness of the air dielectric between the plates, is'notneccssoril-ylinear in proportion to therot-ation or movements of the movablcplates-but may follow any desired curve in orderyto produce 60. theparticular result desired. In theexamples of my invention illustrated inthe accompen ng drawings the thicknags of the plates 0 T able element ofthe stator in minimum capacity position the thinner of theairdielectrics claim.

' Fig. 3 isa detail plates approacheach.

element, or of either one of such elements, 66 varies at diiierentportions of the areas of the plates, as by making the plates taperingfrom one end to another, so that when the rotor plates first enterbetween the stator plates the air dielectrics between the opposingplates may be large, and as the rotor plates continue to interleave withthe stator plates the air dielectrics between the opposing platesgradually decrease until at the point of complete interleaving of theplates the air dielectrics between opposing plates are minimum. Thiseffect is accomplished by so locating the rotor plates respecting thestator plates that when the rotor plates are 7 0 portions of the rotorplates will be located in position to enter between the thinner portionsof the stator plates, so that as the rotor plates are moved for greaterinterleaving with the stator plates the thinner portions of the rotorplates approach the thicker portions of the stator pistes, and thethicker portions of the rotor plates approach the thinner portions ofthe stator plates, for gradually reducing the thickness of the airdielectrics between the opposing plates, and conversely for increasingthe air dielectrics between opposing plates as the rotor is movedreversely.

y invention also comprises details of improvement that will be more(fully hereinafter set forth and then pointe outin the Reference is tobe had to the accompanying drawings forming a part hereof, wherein Fig.1 is a front View of a variable air condenser, the dial being partlybroken away,v illustrating the plates in maximum capacity position;

Fig. 2 is an edge View of Fig. l; I

View, partly in sehtion on lines 3, 3 in Fig. 2, illustrating the rotorplates in partially interleaving position;

Fig. 4 is a detail edge View corresponding to Fig. 2, illustrating therotor plates near a minimum capacity position; Fig. 5 is a detailerspective view of supporting means for the stator plates;

Fig. 6 is a part1 broken side view; 4 Fig. 7 is a detai side viewshowing the plates in the position of Fig.4;

Fig, Sis'a face view of one of tively on lines a, b and c in 8;

Fig. 13 is a perspective view of a stator plate Fig. 14 is a face Viewof a rotor plate; Fig. 15 is an edge view of Fig. 14:; Figs. 16, 17 and18 are respectively sections on lines d, e and f of Fig. 14;

Fig. 19 is a perspective view of the rotor plate; Fig. 20 is a developeddagrammatl c edge view illustrating the varla'ligpn in thlckness of apair of rotor and stator plates;

Fig. 21 is a detail edge view illustrating a modified form of stator-androtor plates;

Fig. 21- is a perspective view of a rotor plate of Fig. 21. i

Fig. 22 is a similar view illustrating another modification of saidplates;

Fig. 23 is an edge view of a further modification ofstator and rotorplates; and

Figs. 24. and 25 are perspective views respectively of stator 'androtorplates in a form modified from that shown .n full lines in Figs. 8 and 14.

Similar numerals of reference indicate corresponding parts in theseveral views.

The main frame of the condenser illustratedcomprises end plates 1, 2,which may be of metal, connected together spaced relation by posts 3,which may be of ordinary or usual construction; At 4 are insulatingstrips or supports extending transversely respecting the end plates 1,2, which strips or supports are shown secured by screws 5' to out turnedears 6, 7 on the end plates 1, 2.

The stator comprises spaced metal plates 8 which are supported by theinsulating strips 4. I have illustratedsupports 9 for the stator plateseach comprising a suitable -mountin block or piece ofmetal having spacedslots 10 to receive the corres onding edge portions of the plates 8, thelocks 9 being provided with longitudinal holes 11 receiving screws 12forretaining the plates between the spaced members 9 of the blocks. Theblocks 9 are shown provided with threaded projections 13 thatpassthrough holes in the. strips 4 and are provided with nuts 14 forsecuring the blocks to'said strips. By preference spacers or washers 15-are mterposed between each strip 4 and the adjacent 'block' 9 forspacing the latter from the strip with an air gap therebetween, asindicated in Fig. 3, to reduce, dielectric losses. A circuit terminal 16is attached to one of the projections 13 for including the statorelement in the circuit.

s The shaft 17 'ofthe rotor element is pivot ally carried by the endplates 1, 2, which shaft may be providedwith any suitable dial or knob18 for rotating the shaft. The shaft 17 carries spaced rotor plates 19that are adapted t o rotate in parallel planes to interleave with thestator plates. The rotor plates may be secured to shaft 17 in anysuitable or well known way "with washers 20 interposed between the rotorplates and spacing them apart. The rotor shaft 17 is shown journaled atone end in a ste screw 21 carried by end plate 1 and in a sieeve 22carried by end plate 2, a spring 23 be ng se cured upon end plate 1 andin operat ve engagement with the rotor shaft, (Fig. 8). As so fardescribed the condenser parts are of a well known type, and may bevaried in construction in any desired way.

In accordance with my invention the lates of the stator, or of therotor, or of bot are so shaped as to vary the thickness of the jdielectric between the plates in various posh tions of the stator androtor. elements relatively to one another. This may be accomplished bymaking the dimension between the surfaces of the plates different invarious thickness of the plates varies at different portions of theirareas, such as by being graduated in thickness from one portion toanother, in tapering shape, and, in some examples illustrated, in such away that the opposite surfaces of a plate will be parallel alongdifferent radii. I have illustrated the edge portions 8 of the statorplates as relatively thin and the edge tively thick, (Figs. 9 an 13),and the edge portions 19 of the rotor plates as relatively thin and theedge ortions 19 as relatively thick, (Figs. 15 an 19), the plates beingso shaped as to taper in decreasing thickness from the edges 8 and 19toward. the edges- 8 and 19 in such a way that, by preference, thesurfaces of the plates are parallel in radial directions, as illusing'.to Figs. 10,,11 and 12 regarding the stator plates, and at d, e, f, inFig. '14, corresponding to Figs. 16, 17 and'l8 regarding the, rotorplates. In the exainple referred to the tapering shape of plates 8 isinn dportions 8 as relaits 'trated at a, b, c, in Fig. 8, correspondcurvilinear or arcuate direction from edge.

85 to edge 8, as along the dotted line a: any

line y; in Fig. 14. In producing the plates," the corner portions 8- ofthe stator plates are ably made with substantially parallel surfaces,.as to fit properly or snugly within the slots 10 of the'blocks orsupports 9, with the'intervening ortions of the supports serving asspacers or the plates, opposing theircorner portions, so that the statorplates relationship although their operating, surfaces are tapering orwedge-like. The censufficiently reduced in thickness, and-prefer-f mayall be maintained in parallel spaced I curvilinear p equal f faces ofthe IQSPGCHVE StBtOI and rotor plates the rotor 35. will be understoodthat-the tween them so that as "plates are sufiicientlythick andprovided with substantially parallel surfaces to fit .pro erly on shaft17 between the opposing was; era 20, so that the rotor plates may all ebe clamped. in a parallel relationship althoughtheir operating-surfacesare tapering .or wedsfedik'e as; before stated. 29 illustrates anedgewise development of plates 8 and 19, showing variation of thicknessat various portions of the plates, the numerals and letters representingthe portions of Figs. 8 and 1'4.

Instead of making the rotor and stator 'plates in ta ering or wedge-liheform in anes, such as along the respective lines w and y in Figs. 8 andis, said plates may vary in thickness in direction from one extreme edveto another, as illus trated in Figs. 21 will 22; in Fig. 21 thecorresponding plates taper or are in wedge-like shape from one end tothe other, as from the end 8* to the end 8 of the stator plates and fromthe end 19 to the end 19 of the rotor plates. In the last named figurethe plates are 25 substantially true wedgelike form with both surfacesinclined to a plane at right angles to the axis of the shaft. In Fi'r.22 one son face of each plate is inclined with respect to the axis ofthe shaft and the other su.--

face of the corresponding plate is in a plane at right angles to theaxis of the shaft. In Fig. 21 the variation of the thickness of theclielectr'c between the different plates is not 1' all portions of theopposing surin different angular positions of the rotor, but as therotor advances from minimum to maximum position the thickness of thedielectric will be decreased and conversely as is rotated reversely. Inthe Iorm shown in Fig. 22 the same result of varying the thickness ofthe dielectric is accon1- plishedas the rotor advances from minimum\toward maximum position, and conversely in the reverse direction ofrotation of the rotor but with less variation in degree of thickness ofdielectric for each degree of angular rotation of the rotor as comparedto Furs. 1 and 21.

plates liaye plain surfaces at 8, l9" and opposite surfaces of suchplates are inclined to a plane at right angles to the axis of shaft 17and to the surfaces 8, 19 respectively. It curved portions of the statorand rotor plates of Fig. will be produced in the manner set forth withrespect. to the curved dotted lines w and 1 in Figs. 8 and 14.

In the forms illustrated in Figs. 8 and 14 when the elements are at ainimmunrcapacity-posit ion the broad surfaces represented by 8 and .19respectively are in juxtaposition and have a relatively largecapacitybethe condenser is rein Fig. 23 portions of the stator and rotorsolved to produce a greater interleaving the capacity may actuallydecrease for a few degrees, and then gradually increase thereafter. Tominimize this initial capacity because of the opposing of the broadsurfaces of the plates the form illustrated in Figs. 24 and 25 isprovided, wherein the thick edge portion l of the rotor element is. cutaway so as to reduce the capacity between such surface the correspondingsurface 8 of stator element 8, and likewise the thin edge portion 8 iscut away or reduced so as to minimise the capacity between 8 and thethin portion 19 of rotor plate 19. the thicker edges 8 and 19 being injuxtaposr tion and the thinner edges 8 and 19 being in juxtapositionwhen the plates are in minimum capacity position. This has theadditional advantage that the rotor plate is more uniformly balancedbecause of the distribution of weight around the axis than in the formillustrated in Figs. 14 and 19. It also 3 the advantage that it is notnecessary to a large variation in dielectric spacing t the low orminimum capacity part of the condenser setting. Some of this gradual increase can be'produced by suitably shaping the contour ofthe plates, asillustrated at 19* and 8 The relative arrangement of the rotor platesrespecting the stator plates is such that the rotor is in minimumcapacity position, (Fig. 4-), the thin portions 19 thereof will opposevthe thin portions 8' of the stator thick portions 19* of the rotorplates will oppose the thick portions 8 of the stator plates, (Fig. 7),in edgewise relation. When the rotor is rotating toward increasincapacity position with the rotor lates moving in parallel planes atvright ang es to the axis of the rotor shaft, the thin portions of therotor plates will begin to advance between the th n portions of thestator plates and astherotation of the rotor is continued in suchdirection the relatively wide air spaces ergaps between the rotor andstator plates will gradually be reduced, and when the rotor plates arein maximum ca tion between the stator plates, air spaces'or gaps betweenthe stator and rotor plates will be at minimum, with the thin portionsof the rotor plates between the thicker portions of the stator plates,and the thicker portions of the rotor plates between the thin portionsof the stator plates. At intermediate points between the maximum andminimum positions of the rotor and stator plates the air gaps willvaryin dimen .sion.

acity posiig. 2),'the

difi'erent elements increases linearly h reason of the interleaving ofthe plates t e capacity of the condenser increases and such capacityincreases further in proportion as the surfaces of the plates approachone another andthe air gaps or dielectrics decrease in dimension betweenthe plates. Hence, a

embodied in a condenser having a' stator and a rotor it will beunderstood that my invention may be included in a, condenser havingtwosets or series of relatively movable plates for varying the capacity.

Having now described my invention what I claim is:

In a variable air condenser a series of spaced stator plates varying inthickness from one edge toward another and provided with portions havingsubstantially parallel surfaces on opposite sides to symmetricallysupport the plates in spaced relation, and supporting means for saidplates having portions between and opposing said corner portions or theplates for maintaining the platesin spaced re ationship with theirsurfaces of varying thickness maintained in corresponding relation. 1ALLEN D. CARDWELL.

